Patent GB-733005-A (GB)
Title: Improvements in or relating to television tuners for receiving vhf and uhf signals
IPC: H03J5/02
Filed: 1953-02-11
Abstract: 733,005. Radio receiving apparatus. STANDARD COIL PRODUCTS CO., Inc. Feb. 11, 1953 [Feb. 27, 1952], No. 3901/63. Class 40 (5). A television receiver for receiving upon both very-high-frequency and ultra-high-frequency channels comprises two turrets, one of which selectively tunes the receiver to the various channels in the V.H.F. band while the other comprises a plurality of radio-frequency tuned circuits and associated local oscillator circuits each of which converts signals received in a respective group of V.H.F. channels from the U.H.F. band to the band of frequencies occupied by the V.H.F. channels, the output from this turret and the circuits associated therewith being applied to the V.H.F. turret and its associated circuits, means being provided for by-passing the U.H.F. circuits when the V.H.F. signals are to be received. General description, Fig. 1. The receiver comprises a fifteen-position turret 10 carrying tuned circuits for selecting each television channel in the V.H.F. band and further circuits not tuned to any particular V.H.F. channel but which when used in conjunction with the U.H.F. circuits of the receiver allow predetermined U.H.F. channels to be received. The turret is mounted upon a shaft 32 and is operated by a knob 33. A further shaft 34 coaxial with shaft 32 is connected to a nine-position turret 11; this comprises circuits which allow the receiver to be tuned to one of eight sub-bands within the U.H.F. band each sub-band (for the general case) comprising ten different contiguous U.H.F. channels. The shaft 34 is operated by a knob 35 and also carries a cam-surface 36. In the ninth position of turret 11 (i.e. the position shown) the cam lifts an operating rod 40 which causes switch 30 to operate so that aerial 80 is connected directly via leads 92, 107 to two of the fixed contacts co-operating with turret 10. Thus for receiving signals upon a V.H.F. channel, the aerial is connected directly to the V.H.F. turret. The received signal is passed by coupling coils tuned to the frequency selected by the setting of the turret 10 to a R.F. amplifier 141 via leads 143, 144. The amplifier output is applied via coils mounted on the turret 10 to a frequency converter 154 to which the output of a local oscillator 140 is also similarly applied. The local oscillator is tuned to the appropriate frequency by a coil mounted upon the turret 10 ; a second coil coupled thereto supplies the oscillator output to converter 154 via leads 160, 161. The converter consequently develops an intermediate-frequency signal which is used in the conventional manner to operate the television receiver. A fine tuning control is provided by the shaft 51 which carries a rotatable dielectric element forming part of a local oscillator fine-tuning condenser. In ultrahigh-frequency reception the knob 35 is turned to select one of the eight U.H.F. sub-bands whereupon by virtue of the spring 41 acting upon the operating rod 40, the switch 30 is changed over so that signals received by aerial 80 are applied over leads 110, 111 to high-pass filter 65 designed to reject V.H.F. signals. The signal passed by the filter 65 is applied to a band preselector 120 which comprises a filter tuned, in conjunction with coils mounted upon the turret 11, to pass the selected U.H.F. subband. The signals within the selected subband are passed to a crystal mixer 66 to which the output from a U.H.F. local oscillator 130 is also applied. The oscillator 130 is tuned to the appropriate frequency by means of associated components mounted on turret 11, so that the mixer output lies within a band of frequencies corresponding to the channels which can be received by the V.H.F. circuits. The mixer output is consequently applied through the switch 30 to the V.H.F. input leads 92, 107, the desired U.H.F. channel out of the band selected by the preselector 120 and local oscillator 130 being selected by appropriate operation of the V.H.F. turrent 10. Description of electrical circuits, Fig. 2. The turrets are shown in developed form in Fig. 2, the individual panels comprising (apart from an exception to be mentioned later) coil formers upon which are wound coils the terminals of which are brought out to contacts on the base of the panel on the side remote from the former, .Figs. 4 and 5 (not shown), the panels being mounted in the turrets with the contacts outermost, Fig. 10. The band pre-selector 120 comprises a filter circuit, the major portion of which is in the fixed portion of the circuit, the different sub-bands being selected by the different coil circuits on the turret which may be connected in parallel therewith. The U.H.F. local oscillator 130 comprises a Hartley oscillator, the fixed portion of which alone oscillates at 470 Mc./s. In order to select a local oscillator frequency higher than this a further coil, e.g. coil 360, mounted upon the turret 11 is connected in parallel with the main coil 340. In order to select a lower frequency a condenser, e.g. condenser 380, is connected in parallel with the coil 340 (this providing the exception referred to above). The coil 340 is connected to the preselector 120 by a link circuit and the resultant signal applied to mixer 66. A further link circuit couples the mixer output through the switch 30 (when the switch is appropriately set) to a selected one of a number of V.H.F. coils mounted on the turret 10. A coil coupled thereto and wound on the same former is connected to the input of R.F. amplifier 141 which is of cascade form as described in Specification 703,946, comprising two series-connected valves, the second valve having an earthed grid. The amplifier output is connected to a further coil mounted on a second former and coupled together with the output from the Collpit's oscillator 140 to a coil connected to the input of the mixer circuit 154. The mixer circuit output is passed through an I.F. filter 270, 271, 272 to the I.F. stages of the receiver. Turret construction and other mechanical details, Fig. 10. The turret contacts 21 engage with fixed contacts 22, Fig. 10 showing an exploded view of the tuning system. Each turret is surrounded by an indexing disc 500, 510 having a plurality of notches which engage with the spring-loaded wheels 620, thus providing a positive location of both turrets in each selectable position. The dielectric member 50 is associated with condenser plates 520, 526, plate 520 being earthed while plate 526 is mounted on an insulated collar. Tuning-knob constructions, Fig. 14. Fig. 14 is an exploded view of one form of tuning-knob assembly. The U.H.F. knob 35 attached to shaft 34 bears numbers 1 to 8 and a blank space corresponding to the eight sub-bands and the V.H.F. position selected by rotation of the U.H.F. turret 11. The V.H.F. knob 33 is mounted in shaft 32 passing within the shaft 34 and has two sets of numbers marked thereon. The outer set, numbers 0 to 9, is associated with a set of windows 730 through which the numbers on the U.H.F. knob may be seen. The inner set corresponds to the twelve V.H.F. channels and comprises numbers 2 to 13 (to gether with numbers 6A, 6B, 6C, which relate to further channels provided by the receiver to permit U.H.F. reception). In front of these knobs is mounted a mask 700 having an aperture 710. A shutter 720 pivoted at 724 is mounted behind the mask and is so arranged that it moves to an upper position uncovering the V.H.F. channel numbers when V.H.F. knob 33 is turned clockwise and moves to a lower position, uncovering the U.H.F. channel numbers when the V.H.F. knob is turned anticlockwise. Thus to tune to a desired U.H.F. channel, the knob 33 is turned anticlockwise until the units digit of the channel number (on the outer scale of the knob 33) is visible through the window 710. The knob 35 is then turned until the tens digit desired is visible through windows 710 and 730. Fine tuning is effected by the knob 52 attached to the shaft 51. For reception of a desired V.H.F. channel, the knob 35 is turned until the blank space thereon shows through the windows 710, 730. The knob 33 is then turned clockwise until the desired channel number is visible through the lower half of the window 710. Fine tuning is then effected as before. It should be noted that owing to the manner in which the channels are numbered V.H.F. channel 7, for example, provides the units digit 3 for the U.H.F. channels so that two sets of numbers are necessary upon the V.H.F. knob 33. Other forms of tuning knob are described. In one of them, the mask 700 is replaced by a mask rotating with the knob 35 and having a plurality of apertures, eight outer ones aligned with the numbers 1 to 8 on the knob 35 and an inner one through which the V.H.F. channel number on the knob 33 are visible. In the V.H.F. position of the knob 35, this latter aperture is at the top of the knob arrangement and the V.H.F. channel number may be seen through it. In all other positions an outer aperture is uppermost so that the corresponding U.H.F. channel number may be seen. In another arrangement the front masking plate is not used;, instead a manually operable member is provided, in one position of which it masks the U.H.F. channel numbers while uncovering them in another position. In other arrangements switches controlled by the rotation of the U.H.F. knob 35 cause the U.H.F. channel numbers to be illuminated from behind except when the knob is in the V.H.F. position when a second lamp is lit illuminating the V.H.F. numerals. Specification 733,003 also is referred to.